Re: apparent problem on linux/s390

On Tue, Dec 07, 2004 at 10:37:36AM +0200, Nicolai Tufar wrote:
> On Mon, 06 Dec 2004 19:15:23 -0500, Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
> >
> > problems apparently with NaNs, infinities and negative zeros.

Sure smells more like an IEEE issue than a postgresql issue (built for
IBM FP rather than IEEE? Dodgy bugs in the emulator?).

> I am the owner of this baby. It is not an actual mainframe,
> it is Hercules emulator running on AthlonXP 2500+ producing
> 20-25 MIPS of pure mainframe horsepower! On bootup Linux
> reports 130 BogoMIPS and OS/390 reports 40 MIPS. We all
> know that mainframe MIPS != mini MIPS. Anyways, a full
> compile of PostgreSQL source takes about 300 minutes.
> I run it overnight.
>
> Hercules is a tested and proved emulator but I have a vague doubt
> that it's IEEE FPU emulation may be slightly different from the
> real iron's one. Are there test suites to check if a linux's
> math functions confirm to the standards. I may need to run one
> of them first.

IIRC older S390s don't do IEEE FP at all, and it's done via traps to
the OS. Are you emulating the S390 IEEE FP hardware option or are you
emulating non-IEEE hardware, with IEEE fixup in OS390?

Paranoia by Dr Kahan is the classic IEEE compliance tester
<http://www.netlib.org/paranoia/> but I've also had a lot of
success with the softlib based tester at
<http://www.jhauser.us/arithmetic/TestFloat.html>.

Cheers,
Steve